This invention relates to magnetic transducers, and particularly to laminated magnetic heads for use with rotating magnetic media.
Magnetic transducers such as magnetic heads for computer disc drives comprise a magnetic material and a winding arranged to induce magnetic flux into a magnetic media adjacent a gap in the transducer (write function) and/or to perceive magnetic flux from an adjacent magnetic media (read function). In a magnetic disc drive, for example, the transducer will typically comprise a C-core and a confronting I-core with a gap between the two cores. A non-magnetic material, such as glass, is usually disposed between the confronting surfaces of the cores, within the gap, to precisely control the magnetic characteristics of the transducer, as well as to provide structural integrity for the transducer.
Three dimensions are critical to the design of the transducer: the gap width, ,which is orthogonal to the length of the track on the media; the gap length, which is parallel to the track; and the gap or throat depth or height, which is normal to both the width and length. The gap width defines the width of the magnetic circuit of the transducer, and hence the width of the track to be recorded onto or perceived from the magnetic media. The gap or throat height, together with the gap width, defines the surface area of the confronting surfaces of the two halves of the magnetic core.
In the digital recording arts, these three gap dimensions are critical to the performance, and data storage density, of the storage apparatus. For example, a relatively large gap width will create large track widths on the magnetic media, thereby diminishing the total number of tracks available on a media of a given size. If the gap length is large, greater magnetic flux is required to perform a recording, thereby requiring strong write signals and increasing the risk of inducing noise onto adjacent tracks. If the gap height is large, a substantial portion of the magnetic flux path will be away from the gap surface and the adjacent media, thereby decreasing the amount of magnetic flux induced into the magnetic media. Consequently, it is desirable to have all three dimensions, gap width, gap length and gap height, be as small as possible, but not so small that data cannot be read or recorded in the media.
Gap heights are typically controlled by tapering an inside surface of the C-core and lapping or polishing the read/write surface of the completed transducer to a controlled thickness. The gap length, which is typically a function of the thickness of the non-magnetic media within the gap, is controlled by the thickness of that media. For example, by depositing glass to a desired thickness, the gap length may be accurately controlled. However, gap width is not so easily controlled.
Typically, gap width is adjusted by grinding or lapping the sides of the cores to a desired gap width. However, material removal to achieve both gap width and gap length is unsatisfactory for high precision transducers for high density recording and read back.
The present invention concerns a laminated magnetic head. Until recently, laminate magnetic heads were known only to the tape recording industry. An example of such a magnetic head is described in the Hanaoka U.S. Pat. No. 4,369,477 issued Jan. 18, 1983. There, the laminate material forms the two legs of a C-core with the magnetic circuit closed by the tape itself. Such magnetic transducers are not adaptable to the disc art because magnetic disc transducers require an I-core to form a gap.
More recently, laminated heads employing laminated C-cores confronting laminated I-cores have been developed for the video tape recording art. Examples of such heads may be found in Gukkenberger et. al. U.S. Pat. No. 4,854,035, Yohda et. al. U.S. Pat. No. 4,890,379, Saito et. al. U.S. Pat. No. 4,894,742, Miyakawa et. al. U.S. Pat. No. 4,899,241, and Satomi et. al. U.S. Pat. No. 4,947,542. However, each of these laminated heads required both a laminated C-core and a laminated I-core which were difficult to align for assembly. Consequently, the manufacturing and assembly procedures were expensive and yielded low yield rates of useable heads, and the resulting head characteristics were difficult to control.